1. Technical Field
The invention disclosed broadly relates to data processing technology and more particularly relates to cryptographic applications in data processing.
2. Background Art
The following two copending patent applications are related to this invention and are incorporated herein by reference: B. Brachtl, et al., "Controlled Use of Cryptographic Keys via Generating Stations Established Control Values", Ser. No. 55,502, filed March 1987 now U.S. Pat. No. 4,850,017 and assigned to IBM Corporation; S. M. Matyas, et al., "Secure Management of Keys Using Control Vectors," filed August 1988, and assigned to IBM Corporation.
Various methods exist in support of electronic data security. Cryptography is the transformation of intelligible information into apparently unintelligible form in order to conceal the information from unauthorized parties. Cryptography is the only known practical method to protect information transmitted through communications networks that use land line, communications satellities, and microwave facilities. It can also be the most economical way to protect stored data. Cryptographic procedures can be used not only to protect the privacy of data, but also the integrity of data.
The cryptographic transformation of data is ordinarily defined by a selected algorithm, or procedure, under the control of a key. Since the algorithm is normally public knowledge, protection of the transformed, or enciphered, data depends on secrecy of the key. Thus the key must be kept secret to prevent an opponent from simply using the known algorithm and key to recover the enciphered data. The protection of the data therefore hinges on the protection of secret keys.
A new approach to key management is described in the above-mentioned copending application by S. M. Matyas, et al. which also provides a good background for this invention. The invention disclosed herein deals with data cryptography which has as its objective the application of cryptographic keys and methods to protecting the confidentiality and integrity of data via cryptography whereas the S. M. Matyas, et al. copending patent application deals with the generation, distribution, and management of the keys themselves.
Prior art methods for encryption and decryption of data have evolved into complex sequences of key and data manipulations to thwart the attacks of an eavesdropper. These sequences have become so convoluted that security management of the secure system is difficult. Changing the security features of a processor or a system of processors is costly. What is needed is a better way to control usage of keys and the data encrypted by those keys. It is important for the system administrator to be able to specify the security features of the system, including the ability to maintain the separation of certain types of data and the corresponding keys. To maximize the security of the system, the administrator should be able to do this on a dynamic, unannounced basis with ease. The system administrator must be able to enforce a security policy for the system which imposes restrictions on the users, the data, the keys and the crytographic operations which can be performed. That enforcement should be easily implemented by the administrator and yet should be secure from subversion by an attacker. The features of flexibility and security have been difficult to achieve in the prior art.